To this end, it is known to provide thermal protection in the form of Juxtaposed unit modules or "tiles" that are fixed on an internal primary structure to be protected of the vehicle. When the vehicle is reusable (space plane or hypersonic airplane), the fixing of the modules must be designed so as to allow a damaged module to be replaced without too much difficulty.
Proposals are made in document FR-A-2 657 675 to provide thermal protection for a space plane by means of juxtaposed quadrangular tiles. Each tile includes a fairing element made of ceramic matrix composite material and a thermal insulator disposed inside the fairing element. This has fixing tabs that are connected to the primary structure to be protected by straps and screws. Such a tile is dismounted by poking a tool by deforming flexible gaskets provided between adjacent tiles.
That known solution does indeed enable a damaged tile to be replaced from the outside, but it presents drawbacks.
Thus, it is necessary to provide a gap of sufficient size between adjacent tiles for it to be possible to pass and drive the tool required for unscrewing the coupling means between the fairing and the fixing strap secured to the primary structure. Even though this gap is filled by means of a gasket, the aerodynamic function of juxtaposed tiles and their thermal protection function are thereby degraded, and any damage to the gaskets, e.g. during assembly, is particularly harmful for these two functions.
In addition, it is necessary between the fairing elements, the straps and the primary structure to insert spacers and washers of thickness that is fitted on demand in order to correct for inevitable defects of shape in these various parts and to ensure continuity of the aerodynamic shape of the aerospace vehicle, thereby making the thermal protection heavier and more complex.
Furthermore, the shape of the gap required for receiving the fixing means between the fairing elements is such that it requires a gasket whose right cross-section is in the form of a varying trapezium, and that is difficult to make.
In addition, differences in thermal expansion between the fairing elements and the primary structure give rise to harmful mechanical stresses at the fastenings.
A support structure for a very high temperature reactor is also known from patent U.S. Pat. No. 4,459,261, which structure comprises link members between the graphite wall of the reactor and a lateral heat shield situated outside the reactor. The link members are constituted by elastically deformable rods that extend horizontally across the gap between the reactor wall and the heat shield to which they are connected by ball-and-socket joints.
Such a structure acts in compression against the wall of the reactor and enables dimensional variations in the horizontal and vertical directions to be accommodated. However, it does not constitute a modular structure enabling a portion of the wall to be removed and replaced easily. In addition, it is necessary, at least on the side of the reactor wall, to provide a ball-and-socket connection that is capable of withstanding high temperatures. Furthermore, the use of resilient link members cannot be entertained when the outside structure needs to be undeformable, which happens to be the case, in particular, for a space plane because of the aerodynamic function that the thermal protection elements must perform.